Methods for epitaxial silicon growth

ABSTRACT

Methods of cleaning substrates and growing epitaxial silicon thereon are provided. Wafers are exposed to a plasma for a sufficient time prior to epitaxial silicon growth, in order to clean the wafers. The methods exhibit enhanced selectivity and reduced lateral growth of epitaxial silicon. The wafers may have dielectric areas that are passivated by the exposure of the wafer to a plasma.

BACKGROUND OF THE INVENTION

[0001] Epitaxial silicon is used in a variety of semiconductor deviceswhen a pure silicon layer is required. Epitaxial silicon is generallygrown on a substrate and exhibits the same crystal structure as thesubstrate on which it is grown. Epitaxial silicon layers may have theirdoping type or concentration controlled independently from the substrateon which the layers are grown. Generally, the substrate on whichepitaxial silicon is to be grown must be cleaned prior to the growth toremove impurities and ensure that the epitaxial silicon layer is of ahigh quality.

[0002] One approach to cleaning substrates prior to epitaxial silicongrowth is to wash the substrate using hydrofluoric acid and tosubsequently hydrogen bake the substrate at high temperatures. However,epitaxial silicon growth on silicon areas cleaned in this manner mayexhibit a high degree of unwanted lateral growth. Additionally,dielectric layers that are subsequently exposed to epitaxial silicongrowth by chemical vapor deposition may exhibit unwanted epitaxialsilicon growth in areas of nucleation in the dielectric layers. Thus,the selectivity of the epitaxial silicon growth process may be low.

[0003] Therefore, there remains a need in the art for epitaxial silicongrowth methods that do not exhibit a high degree of lateral growth.Additionally, there remains a need in the art for epitaxial silicongrowth methods that are selective.

SUMMARY OF THE INVENTION

[0004] These needs are addressed by embodiments of the present inventionthat provide substrate cleaning and epitaxial silicon growth methods.

[0005] In accordance with an embodiment of the present invention, amethod of cleaning a semiconductor surface is provided. The methodcomprises; providing a wafer, wherein the wafer has an upper surface,and wherein the wafer has a silicon area on the upper surface; forming aplasma from a gas flow, wherein the gas flow comprises an etchant gas;and exposing the upper surface of the wafer to the plasma. The exposureof the upper surface of the wafer to the plasma cleans the upper surfaceand renders the silicon area suitable for subsequent epitaxial silicongrowth.

[0006] In accordance with another embodiment of the present invention, amethod of growing epitaxial silicon is provided. The method comprisesproviding a wafer, wherein the wafer has an upper surface, and whereinthe wafer has a silicon area on the upper surface. The method furthercomprises forming a RF plasma from a gas flow, wherein the gas flowcomprises an etchant gas, and exposing the upper surface of the wafer tothe RF plasma. The exposure of the upper surface of the wafer to the RFplasma renders the silicon area suitable for epitaxial silicon growth.The method also comprises growing epitaxial silicon on the silicon areasubsequent to the exposure of the upper surface of the wafer to the RFplasma.

[0007] In accordance with yet another embodiment of the presentinvention, a method of growing epitaxial silicon is provided. The methodcomprises providing a wafer. The wafer has an upper surface, and thewafer has a first silicon area on the upper surface. Additionally, thewafer has a first dielectric area on the upper surface. The methodfurther comprises forming a RF plasma from a gas flow, wherein the gasflow comprises at least one etchant gas. The method comprises exposingthe upper surface of the wafer to the RF plasma. The exposure of theupper surface of the wafer to the RF plasma renders the first siliconarea suitable for epitaxial silicon growth. The method also comprisesgrowing epitaxial silicon on the first silicon area subsequent to theexposure of the upper surface of the wafer to the RF plasma. Theepitaxial silicon growth exhibits selectivity of growth on the firstsilicon area over the first dielectric area, and the selectivity ofgrowth is enhanced by the exposure of the upper surface of the wafer tothe RF plasma.

[0008] In accordance with another embodiment of the present invention, amethod of growing epitaxial silicon is provided. The method comprisesproviding a wafer. The wafer has an upper surface. The wafer has a firstsilicon area on the upper surface, and the wafer has a first dielectricarea on the upper surface. The method comprises forming a RF plasma froma gas flow, wherein the gas flow comprises at least one etchant gas. Themethod further comprises exposing the upper surface of the wafer to theRF plasma, wherein the exposure of the upper surface of the wafer to theRF plasma renders the first silicon area suitable for epitaxial silicongrowth. The method comprises growing epitaxial silicon on the firstsilicon area subsequent to the exposure of the upper surface of thewafer to the RF plasma. The epitaxial silicon grows at a lateral growthrate and a vertical growth rate. The lateral growth rate of theepitaxial silicon is reduced relative to the vertical growth rate by theexposure of the upper surface of the wafer to the RF plasma.

[0009] In accordance with another embodiment of the present invention, amethod of growing epitaxial silicon is provided. The method comprisescleaning a surface having a dielectric area adjacent to a silicon areawith a RF plasma formed from a gas flow having an etchant gas andgrowing epitaxial silicon on the cleaned surface. The epitaxial silicongrowth exhibits selectivity of growth on the silicon area over thedielectric area, and the selectivity of growth is enhanced by thecleaning of the surface. The epitaxial silicon grows at a lateral growthrate and a vertical growth rate over the silicon area, and the lateralgrowth rate of the epitaxial silicon is reduced relative to the verticalgrowth rate by the cleaning of the surface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010]FIGS. 1A-1B are cross sectional views of epitaxial silicon growthin accordance with an embodiment of the present invention.

[0011]FIG. 2 is a flow diagram of process steps for epitaxial silicongrowth in accordance with the embodiments of the present invention.

[0012]FIGS. 3A-3B are cross sectional views of epitaxial silicon growthin accordance with another embodiment of the present invention.

[0013]FIGS. 4A-4B are cross sectional views of epitaxial silicon growthin accordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention is directed to methods of cleaningsubstrates and growing epitaxial silicon thereon. The methods expose thesubstrates to a plasma prior to epitaxial silicon growth. The methodsexhibit a high degree of selectivity and a low degree of lateral growthof epitaxial silicon layers.

[0015] In the following detailed description of the preferredembodiments, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration, and not byway of limitation, specific preferred embodiments in which the inventionmay be practiced. It is to be understood that other embodiments may beutilized and that logical, mechanical, and electrical changes may bemade without departing from the spirit and scope of the presentinvention. In the drawings, like numerals describe substantially similarcomponents throughout the several views.

[0016] Referring to FIGS. 1A, 1B, and 2, a method of growing epitaxialsilicon is illustrated. The method includes the step 20 of providing awafer 10. For purposes of defining and describing the present invention,the term “wafer” is defined to mean any composition or constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive material such as a semiconductive wafer, either alone orin assemblies comprising other materials thereon, and semiconductivematerial layers, either alone or in assemblies comprising othermaterials. The wafer 10 generally has an upper surface 12 and a lowersurface 14. Additionally, the wafer 10 has a silicon area 16 on theupper surface 12. For purposes of defining and describing the presentinvention, the term “silicon area” is defined to mean an area containingsilicon or polysilicon, whether doped or undoped.

[0017] A plasma is formed from a gas flow in step 22, and upper surface12 of the wafer 10 is exposed to the plasma in step 24. Generally, theplasma is a radio frequency (RF) plasma that is formed by applying an RFpower to the gas flow. The gas flow contains at least one etchant gas.The etchant gas is selected to contain a species that may be ionized inthe plasma and that may etch the wafer 10. For example, the etchant gasmay be a gas containing a halogen. Suitable etchant gases include, butare not limited to F₂, C1 ₂, CF₄, SF₆, and the like. The RF plasma maybe formed in a processing chamber, and the wafer 10 may be provided inthe processing chamber during steps 20, 22, and 24. For example, thewafer 10 may be provided in a single wafer processing chamber.Alternatively, the wafer 10 may be provided in a batch processingchamber. Subsequent epitaxial silicon growth, as described hereinafter,may be carried out in the same or a different processing chamber as theexposure of the wafer 10 to the plasma in step 24. Generally, theepitaxial silicon growth is carried out in the same processing chamber.

[0018] The RF plasma is generally a low power plasma that etches theupper surface 12 of the wafer and removes unwanted contaminants andoxide from the upper surface 12. For example, when SF₆ is used as thegas flow, the RF power may be between about 300 to about 450 W. The gasflow may have a flow rate of between about 30 to about 40 standard cubiccentimeters per minute (sccm). The background pressure may be betweenabout 10⁻⁶ to about 10⁻⁸ Torr. The wafer 10 may be exposed to the RFplasma for between about 1 second to about 2 minutes.

[0019] Once the upper surface 12 of the wafer 10 has been exposed to theplasma for a sufficient time, the upper surface 12 is cleaned, and thesilicon areas 16 are generally rendered suitable for subsequentepitaxial silicon growth. It will be understood that the upper surface12 may have a plurality of silicon areas 16, and the exposure of thewafer 10 to the plasma will render the plurality of silicon areassuitable for subsequent epitaxial silicon growth. After the wafer 10 hasbeen exposed to the plasma, epitaxial silicon 18 may be grown on thesilicon area 16 as illustrated by step 26. The epitaxial silicon 18 maybe grown using any suitable growth method. For example, the epitaxialsilicon 18 may be grown using a suitable chemical vapor deposition (CVD)method. The epitaxial silicon 18 is generally of high quality. It willbe understood that “epitaxial silicon” may be used to refer to epitaxialsilicon or epitaxial polysilicon that is grown on silicon or polysiliconareas respectively.

[0020] Referring to FIGS. 2, 3A and 3B, a method of growing epitaxialsilicon is illustrated. The method includes the step 20 of providing awafer 10. The wafer 10 has an upper surface 12. The wafer 10 has atleast one silicon area 16 on the upper surface 12, and the wafer 10 hasat least one dielectric area 30 on the upper surface 12. The dielectricareas 30 may be any suitable dielectric. For example, the dielectricareas 30 may be silicon oxide, silicon nitride, or combinations thereof.A RF plasma is formed in step 22 as described herein, and the uppersurface 12 of the wafer 10 is exposed to the plasma in step 24. Theexposure of the upper surface 12 of the wafer 10 to the plasma in step24 renders the silicon areas 16 suitable for epitaxial silicon growth.Additionally, the exposure of the upper surface of the wafer 10 to theplasma in step 24 passivates a surface 32 of the dielectric areas 30.

[0021] Epitaxial silicon 18 is grown on the silicon areas 16 as shown instep 26 subsequent to step 24. The epitaxial silicon 18 is grown in aselective manner because it generally grows only the silicon areas 16 onthe upper surface 12 of the wafer 10 and does not grow significantly onthe dielectric areas 30. Epitaxial silicon growth on the dielectricareas 30 is substantially prevented by the exposure of the upper surface12 of the wafer 10 to the plasma because the surface 32 has beenpassivated, and epitaxial silicon does not grow as readily on thesurface of the passivated dielectric because nucleation centers may notform as readily during growth. Thus, the selectivity of the epitaxialsilicon growth method is increased by the exposure of the wafer 10 tothe plasma in step 24. The dielectric areas 30 may serve as mask areasthat may be subsequently removed in later processing steps as desired.

[0022] Referring to FIGS. 2, 4A, and 4B, a method of growing epitaxialsilicon is illustrated. The method includes providing a wafer 10 in step20, and the wafer 10 has an upper surface 12. The wafer 10 has at leastone silicon area 16 on the upper surface 12, and the wafer 10 has atleast one dielectric area 30 on the upper surface 12. The dielectricarea 30 is adjacent to the silicon area 16. A RF plasma is formed instep 22, and the upper surface 12 of the wafer 10 is exposed to the RFplasma in step 24. The silicon area 16 is rendered suitable forepitaxial silicon growth by the exposure of the upper surface 12 to theplasma.

[0023] Epitaxial silicon 18 is grown on the silicon area 16 in step 26subsequent to step 24. The epitaxial silicon 18 grows in a verticaldirection 34 and in a lateral direction 36. The growth in the verticaldirection 34 exhibits a vertical growth rate, and the growth in thelateral direction 36 exhibits a lateral growth rate. The lateral growthrate is reduced relative to the vertical growth rate by the exposure ofthe upper surface 12 of the wafer 10 to the RF plasma. It is believedthat the condition of the surface bonds of the dielectric area 30 arechanged by the RF plasma, and the lateral growth 36 of the epitaxialsilicon is thus inhibited.

[0024] Steps 22 and 24 may be controlled in any suitable manner toprovide a desired reduction in the lateral growth rate when theepitaxial silicon 18 is grown in step 26. For example, the lateralgrowth rate may have a ratio to the vertical growth rate of betweenabout 1:1 to about 1:8. More generally, the lateral growth rate may havea ratio to the vertical growth rate of between about 1:4 to about 1:8.Thus, lateral growth of the epitaxial silicon 18 may be reduced over theadjacent dielectric area 30. It will be understood that the wafer 10 mayhave a plurality of silicon areas 16 and a plurality of dielectric areas30 on an upper surface 12.

[0025] In order that the invention may be more readily understood,reference is made to the following examples, which are intended to beillustrative of the invention, but are not intended to be limiting inscope.

EXAMPLE 1

[0026] A wafer having silicon areas and silicon nitride areas on anupper surface was exposed to a RF plasma formed from an SF₆ gas flowflowing at 40 sccm. The RF power was 300 W, and the wafer was exposed tothe plasma for 60 seconds.

[0027] Epitaxial silicon was subsequently grown on the silicon areas.The epitaxial silicon was grown by a SiH₆, Cl₂, and H₂ gas flow presentwith a 10⁻⁸ Torr background pressure. The growth was continued forbetween about 5 to about 25 minutes in order to achieve a desiredthickness of epitaxial silicon. The nitride areas did not exhibitsignificant epitaxial silicon growth, and it was apparent that the RFplasma had passivated the surface of the nitride.

EXAMPLE 2

[0028] A wafer having polysilicon areas and silicon nitride areas on anupper surface was exposed to a RF plasma formed from an SF₆ gas flowflowing at 40 sccm. The RF power was 300 W, and the wafer was exposed tothe plasma for 60 seconds.

[0029] Epitaxial polysilicon was subsequently grown on the siliconareas. The epitaxial silicon was grown by a SiH₆, Cl₂, and H₂ gas flowpresent with a 10⁻⁸ Torr background pressure. The growth was continuedfor between about 5 to about 25 minutes in order to achieve a desiredthickness of epitaxial polysilicon. The nitride areas did not exhibitsignificant epitaxial polysilicon growth, and it was apparent that theRF plasma had passivated the surface of the nitride.

EXAMPLE 3

[0030] A wafer having silicon areas and silicon oxide areas on an uppersurface was exposed to a RF plasma for 60 seconds. The plasma was formedfrom a 40 sccm gas flow of SF₆, and the RF power was 300 W.

[0031] Epitaxial silicon was grown on the silicon areas by a SiH₆, Cl₂,and H₂ gas flow present with a 10⁻⁸ Torr background pressure. The growthwas continued for between about 5 to about 25 minutes in order toachieve a desired thickness of epitaxial silicon. The epitaxial siliconexhibited a lateral growth rate to vertical growth rate ratio of about1:4, as measured by comparing the height of the vertical growth to thewidth of the lateral growth.

[0032] It will be apparent to those skilled in the art that variouschanges may be made without departing from the scope of the invention,which is not to be considered limited to what is described in thespecification.

What is claimed is:
 1. A method of cleaning a semiconductor surface,comprising: providing a wafer, wherein said wafer has an upper surface,and wherein said wafer has a silicon area on said upper surface; forminga plasma from a gas flow, wherein said gas flow comprises an etchantgas; and exposing said upper surface of said wafer to said plasma,wherein said exposure of said upper surface of said wafer to said plasmacleans said upper surface and renders said silicon area suitable forsubsequent epitaxial silicon growth.
 2. The method as claimed in claim 1wherein said upper surface of said wafer has a plurality of siliconareas thereon, and wherein said exposure of said wafer to said plasmarenders said plurality of silicon areas suitable for subsequentepitaxial silicon growth.
 3. A method of growing epitaxial silicon,comprising: providing a wafer, wherein said wafer has an upper surface,and wherein said wafer has a silicon area on said upper surface; forminga RF plasma from a gas flow, wherein said gas flow comprises an etchantgas; exposing said upper surface of said wafer to said RF plasma,wherein said exposure of said upper surface of said wafer to said RFplasma renders said silicon area suitable for epitaxial silicon growth;and growing epitaxial silicon on said silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma.
 4. Themethod as claimed in claim 3 wherein said etchant gas comprises a gascontaining a halogen.
 5. The method as claimed in claim 3 wherein saidetchant gas comprises SF_(6.)
 6. The method as claimed in claim 5wherein said etchant gas has a gas flow rate of between about 30 toabout 40 sccm.
 7. The method as claimed in claim 5 wherein said RFplasma is formed using an RF power of between about 300 to about 450 W.8. The method as claimed in claim 5 wherein said upper surface of saidwafer is exposed to said RF plasma for about 1 second to about 2minutes.
 9. A method of growing epitaxial silicon, comprising: providinga wafer in a processing chamber, wherein said wafer has an uppersurface, and wherein said wafer has a silicon area on said uppersurface; forming a RF plasma from a gas flow, wherein said gas flowcomprises an etchant gas, and wherein said RF plasma is formed in saidprocessing chamber; exposing said upper surface of said wafer to said RFplasma in said processing chamber, wherein said exposure of said uppersurface of said wafer to said RF plasma renders said silicon areasuitable for epitaxial silicon growth; and growing epitaxial silicon onsaid silicon area subsequent to said exposure of said upper surface ofsaid wafer to said RF plasma, wherein said epitaxial silicon is grown insaid processing chamber.
 10. A method of growing epitaxial silicon,comprising: providing a wafer, wherein: said wafer has an upper surface;said wafer has a first silicon area on said upper surface; and saidwafer has a first dielectric area on said upper surface; forming a RFplasma from a gas flow, wherein said gas flow comprises at least oneetchant gas; exposing said upper surface of said wafer to said RFplasma, wherein said exposure of said upper surface of said wafer tosaid RF plasma renders said first silicon area suitable for epitaxialsilicon growth; growing epitaxial silicon on said first silicon areasubsequent to said exposure of said upper surface of said wafer to saidRF plasma, wherein: said epitaxial silicon growth exhibits selectivityof growth on said first silicon area over said first dielectric area;and said selectivity of growth is enhanced by said exposure of saidupper surface of said wafer to said RF plasma.
 11. A method of growingepitaxial silicon, comprising: providing a wafer, wherein: said waferhas an upper surface; said wafer has a first silicon area on said uppersurface; said wafer has a first dielectric area on said upper surface;and said first dielectric area has a surface; forming a RF plasma from agas flow, wherein said gas flow comprises at least one etchant gas;exposing said upper surface of said wafer to said RF plasma, whereinsaid exposure of said upper surface of said wafer to said RF plasmarenders said first silicon area suitable for epitaxial silicon growth;said exposure of said upper surface of said wafer to said RF plasmapassivates said surface of said first dielectric area; selectivelygrowing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma.
 12. Themethod as claimed in claim 11 wherein said first dielectric areacomprises a mask area.
 13. The method as claimed in claim 11 whereinsaid dielectric comprises silicon oxide.
 14. The method as claimed inclaim 11 wherein said dielectric comprises silicon nitride.
 15. Themethod as claimed in claim 11 wherein said first silicon area comprisesa polysilicon area.
 16. The method as claimed in claim 11 wherein saidfirst silicon area comprises a silicon area.
 17. The method as claimedin claim 11 wherein said upper surface of said wafer comprises aplurality of silicon areas, and wherein said upper surface of said wafercomprises a plurality of dielectric areas.
 18. A method of growingepitaxial silicon, comprising: providing a wafer, wherein: said waferhas an upper surface; said wafer has a first silicon area on said uppersurface; said wafer has a first dielectric area on said upper surface;and said first dielectric area has a surface; forming a RF plasma from agas flow, wherein said gas flow comprises at least one etchant gas;exposing said upper surface of said wafer to said RF plasma, whereinsaid exposure of said upper surface of said wafer to said RF plasmarenders said first silicon area suitable for epitaxial silicon growth;said exposure of said upper surface of said wafer to said RF plasmapassivates said surface of said first dielectric area; selectivelygrowing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma, whereinsaid epitaxial silicon growth on said first dielectric area issubstantially prevented by said exposure of said upper surface of saidwafer to said RF plasma.
 19. A method of growing epitaxial silicon,comprising: providing a wafer, wherein: said wafer has an upper surface;said wafer has a first silicon area on said upper surface; and saidwafer has a first dielectric area on said upper surface; forming a RFplasma from a gas flow, wherein said gas flow comprises at least oneetchant gas; exposing said upper surface of said wafer to said RFplasma, wherein said exposure of said upper surface of said wafer tosaid RF plasma renders said first silicon area suitable for epitaxialsilicon growth; growing epitaxial silicon on said first silicon areasubsequent to said exposure of said upper surface of said wafer to saidRF plasma, wherein: said epitaxial silicon grows at a lateral growthrate and a vertical growth rate; and said lateral growth rate of saidepitaxial silicon is reduced relative to said vertical growth rate bysaid exposure of said upper surface of said wafer to said RF plasma. 20.A method of growing epitaxial silicon, comprising: providing a wafer,wherein: said wafer has an upper surface and a lower surface; said waferhas a first silicon area on said upper surface; and said wafer has afirst dielectric area on said upper surface adjacent to said firstsilicon area; forming a RF plasma from a gas flow, wherein said gas flowcomprises at least one etchant gas; exposing said upper surface of saidwafer to said RF plasma, wherein said exposure of said upper surface ofsaid wafer to said RF plasma renders said first silicon area suitablefor epitaxial silicon growth; growing epitaxial silicon on said firstsilicon area subsequent to said exposure of said upper surface of saidwafer to said RF plasma, wherein: said epitaxial silicon grows at alateral growth rate and a vertical growth rate; and said lateral growthrate of said epitaxial silicon is reduced relative to said verticalgrowth rate by said exposure of said upper surface of said wafer to saidRF plasma.
 21. A method of growing epitaxial silicon, comprising:providing a wafer, wherein: said wafer has an upper surface; said waferhas a first silicon area on said upper surface; and said wafer has afirst dielectric area on said upper surface adjacent to said firstsilicon area; forming a RF plasma from a gas flow, wherein said gas flowcomprises at least one etchant gas; exposing said upper surface of saidwafer to said RF plasma, wherein said exposure of said upper surface ofsaid wafer to said RF plasma renders said first silicon area suitablefor epitaxial silicon growth; growing epitaxial silicon on said firstsilicon area subsequent to said exposure of said upper surface of saidwafer to said RF plasma, wherein: said epitaxial silicon grows at alateral growth rate and a vertical growth rate; said lateral growth rateof said epitaxial silicon is reduced relative to said vertical growthrate by said exposure of said upper surface of said wafer to said RFplasma; and said lateral growth rate has a ratio to said vertical growthrate of between about 1:1 to about 1:8.
 22. The method as claimed inclaim 21 wherein said lateral growth rate has a ratio to said verticalgrowth rate of between about 1:4 to about 1:8.
 23. A method of growingepitaxial silicon, comprising: providing a wafer, wherein: said waferhas an upper surface; said wafer has a first silicon area on said uppersurface; and said wafer has a first dielectric area on said uppersurface adjacent to said first silicon area; forming a RF plasma from agas flow, wherein said gas flow comprises at least one etchant gas;exposing said upper surface of said wafer to said RF plasma, whereinsaid exposure of said upper surface of said wafer to said RF plasmarenders said first silicon area suitable for epitaxial silicon growth;growing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma, wherein:said epitaxial silicon grows at a lateral growth rate and a verticalgrowth rate; and said lateral growth rate of said epitaxial silicon isreduced relative to said vertical growth rate by said exposure of saidupper surface of said wafer to said RF plasma, such that lateral growthof said epitaxial silicon is reduced over said first dielectric area.24. A method of growing epitaxial silicon, comprising: providing awafer, wherein: said wafer has an upper surface; said wafer has a firstsilicon area on said upper surface; said wafer has a first dielectricarea on said upper surface adjacent to said first silicon area; and saidfirst dielectric area has a surface; forming a RF plasma from a gasflow, wherein said gas flow comprises at least one etchant gas; exposingsaid upper surface of said wafer to said RF plasma, wherein saidexposure of said upper surface of said wafer to said RF plasma renderssaid first silicon area suitable for epitaxial silicon growth; saidexposure of said upper surface of said wafer to said RF plasmapassivates said surface of said first dielectric area; selectivelygrowing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma, wherein:said epitaxial silicon growth on said first dielectric area is reducedby said exposure of said upper surface of said wafer to said RF plasma;said epitaxial silicon grows at a lateral growth rate and a verticalgrowth rate; and said lateral growth rate of said epitaxial silicon isreduced relative to said vertical growth rate by said exposure of saidupper surface of said wafer to said RF plasma.
 25. A method forselectively growing epitaxial silicon, comprising: cleaning a surfacewith a RF plasma formed from a gas flow having an etchant gas; andgrowing epitaxial silicon on said cleaned surface.
 26. A method forselectively growing epitaxial silicon, comprising: cleaning a surfacehaving a dielectric area and a silicon area with a RF plasma formed froma gas flow having an etchant gas; and growing epitaxial silicon on saidcleaned surface, wherein: said epitaxial silicon growth exhibitsselectivity of growth on said silicon area over said dielectric area;and said selectivity of growth is enhanced by said cleaning of saidsurface.
 27. A method for reducing lateral growth of epitaxial silicon,comprising: cleaning a surface having a dielectric area adjacent to asilicon area with a RF plasma formed from a gas flow having an etchantgas; and growing epitaxial silicon on said cleaned surface, wherein:said epitaxial silicon grows at a lateral growth rate and a verticalgrowth rate over said silicon area; and said lateral growth rate of saidepitaxial silicon is reduced relative to said vertical growth rate bysaid cleaning of said surface.
 28. A method for growing epitaxialsilicon, comprising: cleaning a surface having a dielectric areaadjacent to a silicon area with a RF plasma formed from a gas flowhaving an etchant gas; and growing epitaxial silicon on said cleanedsurface, wherein: said epitaxial silicon growth exhibits selectivity ofgrowth on said silicon area over said dielectric area; said selectivityof growth is enhanced by said cleaning of said surface; said epitaxialsilicon grows at a lateral growth rate and a vertical growth rate oversaid silicon area; and said lateral growth rate of said epitaxialsilicon is reduced relative to said vertical growth rate by saidcleaning of said surface.